Wholly aromatic polyester resins long have been known. For instance, 4-hydroxybenzoic acid homopolymer and copolymers have been provided in the past and are commercially available. Those wholly aromatic polyesters normally encountered in the prior art have tended to be somewhat intractable in nature and to present substantial difficulties if one attempts to melt process the same while employing conventional melt processing procedures. Such polymers commonly are crystalline in nature, relatively high melting or possess a decomposition temperature which is below the melting point, and when molten frequently exhibit an isotropic melt phase. Molding techniques such as compression molding or sintering may be utilized with such materials; however, injection molding, melt spinning, etc., commonly have not been viable alternatives or when attempted commonly have been accomplished with difficulty.
Representative publications which discuss wholly aromatic polyesters include: (a) Polyesters of Hydroxybenzoic Acids, by Russell Gilkey and John R. Caldwell, J. of Applied Polymer Sci., Vol. II, Pages 198 to 202 (1959), (b) Polyarylates (Polyesters From Aromatic Dicarboxylic Acids and Bisphenols), by G. Bier, Polymer, Vol. 15, Pages 527 to 535 (August 1974), (c) Aromatic Polyester Plastics, by S. G. Cottis, Modern Plastics, Pages 62 to 63 (July 1975), and (d) Poly(p-Oxybenzoyl Systems): Homopolymer for Coatings: Copolymers for Compression and Injection Molding, by Roger S. Storm and Steve G. Cottis, Coatings Plast. Preprint, Vol. 34, No. 1, Pages 194 to 197 (April 1974). See also, U.S. Pat. Nos. 3,039,994; 3,169,121; 3,321,437; 3,553,167; 3,637,595; 3,651,014; 3,723,388; 3,759,870; 3,767,621; 3,778,410; 3,787,370; 3,790,528; 3,829,406; 3,890,256; and 3,975,487.
Also, it more recently has been disclosed that certain polyesters may be formed which exhibit melt anisotropy. See for instance, (a) Polyester X7G-A Self Reinforced Thermoplastic, by W. J. Jackson Jr., H. F. Kuhfuss, and T. F. Gray, Jr., 30th Anniversary Technical Conference, 1975 Reinforced Plastics/Composites Institute. The Society of the Plastics Industry, Inc., Section 17-D, Pages 1 to 4, (b) Belgian Pat. Nos. 828,935 and 828,936, (c) Dutch Pat. No. 7505551, (d) West German Pat. Nos. 2520819, 2520820, and 2,722,120, (e) Japanese Pat. No. 43-223, (f) U.S. Pat. Nos. 3,991,013; 3,991,014; 4,057,597; 4,067,852; 4,075,262; 4,083,829; 4,118,372; 4,130,545; and 4,130,702. See also commonly assigned U.S. Ser. Nos. 843,933, filed Oct. 20, 1977 (now U.S. Pat. No. 4,161,470); and 877,917, filed Feb. 15, 1978.
U.S. Pat. No. 4,067,852, assigned to Celanese Corporation, discloses a wholly aromatic polyester consisting essentially of the recurring units (a) 4-oxybenzoyl moiety, (b) 2,6-dicarboxynaphthalene moiety, and (c) symmetrical dioxy aryl moiety (as defined therein). U.S. Pat. No. 4,083,829, also assigned to Celanese Corp., discloses a wholly aromatic polyester consisting essentially of the recurring units (a) 4-oxybenzoyl moiety, (b) 2,6-dicarboxynaphthalene moiety, (c) symmetrical dioxy aryl moiety (as defined therein), and (d) isophthaloyl and/or meta-dioxy phenylene moiety. These patents can be distinguished from the present invention in that the present invention does not include the use of a 2,6-dicarboxynaphthalene moiety. Neither of the above-mentioned patents specifically discloses the use of 2,6-dihydroxyanthraquinone, which is believed to be the novel feature of the present invention.
It is an object of the present invention to provide a melt processable wholly aromatic polyester.
It is an object of the present invention to provide a wholly aromatic polyester, having a low degree of crystallinity in the solid phase, which forms an anisotropic melt phase.
It is an object of the present invention to provide a melt processable aromatic polyester capable of forming a anisotropic melt phase at a temperature below approximately 375.degree. C., and preferably below approximately 350.degree. C.
It is an object of the present invention to provide a wholly aromatic polyester having high thermal stability.
It is an object of the present invention to provide a wholly aromatic polyester which exhibits an anisotropic melt which is highly tractable.
It is an object of the present invention to provide a wholly aromatic polyester which may be melt spun to form a high-strength fiber having superior properties.
It is an object of the present invention to provide a wholly aromatic polyester which readily may be injection molded to form a molded article exhibiting superior properties (tensile strength, flex strength, impact strength).
It is an object of the present invention to provide a wholly aromatic polyester which exhibits good hydrolytic stability.
These and other objects of the invention will be apparent from the following detailed description and appended claims.